A fuel cell stack consists of hundreds of unit cells, and for each of hundreds of channels, each of which is formed by tying these two to four cells in a bundle, an average cell voltage is sensed by a device in a vehicle. This device is referred to as an SVM (Stack Voltage Monitor) that plays an important role in monitoring performance of each individual cell of the fuel cell stack.
If the average cell voltage of a specific channel (formed by tying four cells) is lower than normal (if a cell leak occurs), there is a strong possibility that a voltage of one cell may drop in practice since gas is not properly supplied thereto due to deterioration of, or flooding in, the stack. In this case, the cell is seriously damaged due to an inverse voltage generated by continuous extraction of a current from the cell, resulting in rapid deterioration of the cell. To prevent this, a fuel cell control unit (FCU) controls a cell so as to prevent secondary damage of the cell by limiting a current.
However, the cell leak is often not prevented by the current limit of the FCU since the cell leak is fast. In this case, the cell leak may occur at a time opposite to that of a maximum current limit. Because of this, the current limit may not be imposed while the cell leak occurs, whereas the current limit may be imposed while the cell leak does not occur. Due to repetition of such a situation the vehicle may exhibit abnormal behavior such as lurching.
Accordingly, there is a need for a control method of preventing abnormal behavior of a vehicle by sensing a sign of cell leak in advance and performing a suitable current limit at an appropriate time.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.